Silicone rubber composition, silicone rubber, and silicone rubber foam

Abstract

To inhibit the decomposition of silicone rubber into combustible low-molecular siloxane at high temperatures, and suppress weight loss.SOLUTION: This silicone rubber composition comprises: polyorganosiloxane represented by formula (A1) (component a); a weight loss inhibitor (component b); and an organic peroxide crosslinking agent (component c), wherein the weight loss observed when the silicone rubber obtained by crosslinking a silicone rubber composition is heated from 30°C to 900°C at a temperature increase rate of 150°C / minute under a nitrogen atmosphere is less than 0.4 g / cm3.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a silicone rubber composition, a silicone rubber, and a silicone rubber foam. [Background technology]

[0002] The silicone rubber composition contains at least polyorganosiloxane and a crosslinking agent, and the crosslinking agent crosslinks the polyorganosiloxane to form a crosslinked silicone rubber. The silicone rubber composition also contains a foaming agent in addition to the polyorganosiloxane and the crosslinking agent, and the silicone rubber composition is crosslinked and foamed to obtain a silicone rubber foam. Silicone rubber is a material with excellent properties such as weather resistance and heat resistance, and is used in various fields.

[0003] In recent years, in order to improve the flame retardancy of silicone rubber, techniques have been proposed in which various flame retardants are added to silicone rubber compositions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 44-2591 [Patent Document 2] Japanese Patent Application Laid-open No. 48-96650 [Patent Document 3] Japanese Patent Application Publication No. 53-130753, [Patent Document 4] JP 2004-149693 A [Patent Document 5] JP 2009-144024 A, Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the past, when silicone rubber was exposed to high temperatures, it may decompose. This may result in the generation of flammable low molecular weight siloxane, which may reduce the weight of the silicone rubber. Therefore, in order to improve safety, it is necessary to suppress the generation of flammable low molecular weight siloxane.

[0006] Therefore, an object of the present invention is to provide a silicone rubber composition, silicone rubber, and silicone rubber foam that can inhibit the decomposition of flammable low molecular weight siloxanes from silicone rubber at high temperatures and effectively inhibit weight loss of the silicone rubber. [Means for solving the problem]

[0007] The silicone rubber composition of the present invention contains (component a), (component b), and (component c). (Component a) is a polyorganosiloxane represented by the following formula (A1).

[0008] [ka] (In formula (A1), R 1 represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an aliphatic unsaturated group, and R 2 represents an alkenyl group, R 3 are independent R 1 or R 2 where n and m indicate the total number of repeating units that have been randomly polymerized or block polymerized, respectively, and n+m+2, which is the sum of n and m and the number of terminal groups (2), indicates the mass average degree of polymerization. In addition, (component a) has a mass average degree of polymerization of 1,000 or more and 10,000 or less, and R 2 The content per mass is 0.001 mmol / g or more and less than 2.0 mmol / g, and R 2(Component b) is a weight loss inhibitor. (Component c) is an organic peroxide crosslinking agent. In the silicone rubber composition, when a silicone rubber obtained by crosslinking the silicone rubber composition is heated from 30°C to 900°C at a temperature increase rate of 150°C / min in a nitrogen atmosphere, the weight loss is 0.4 g / cm 3 It will be less than. Effect of the Invention

[0009] The present invention can provide a silicone rubber composition, silicone rubber, and silicone rubber foam that can effectively prevent the decomposition of flammable low molecular weight siloxanes from silicone rubber at high temperatures and prevent the weight of the silicone rubber from decreasing. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 shows the relationship between the weight loss WM (g / cm3) of the silicone rubber and the proportion CL (ppm) of platinum atoms in the platinum compound (component c) relative to the polyorganosiloxane (component a) for each example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [A] Silicone rubber composition The silicone rubber composition of this embodiment contains (component a) polyorganosiloxane, (component b) weight loss inhibitor, and (component c) crosslinking agent. In addition, the silicone rubber composition of this embodiment preferably contains (component d) reinforcing silica. As a result, in the silicone rubber composition of this embodiment, the polyorganosiloxane (component a) is crosslinked by the crosslinking agent (component c) to form a silicone rubber that is a crosslinked product of the polyorganosiloxane. In the silicone rubber composition of this embodiment, when the silicone rubber crosslinked from the silicone rubber composition is heated from 30°C to 900°C at a heating rate of 150°C / min in a nitrogen atmosphere, the weight loss is 0.4 g / cm. 3 It will be less than.

[0012] When a silicone rubber foam is obtained as the silicone rubber, the silicone rubber composition of the present embodiment further contains (component e) a foaming agent, which crosslinks and foams the silicone rubber composition of the present embodiment to obtain the silicone rubber foam.

[0013] As described in more detail below, the silicone rubber composition of the present embodiment can inhibit the decomposition of flammable low molecular weight siloxanes from the silicone rubber at high temperatures, and effectively inhibit weight loss of the silicone rubber.

[0014] The components constituting the silicone rubber composition of this embodiment will be described in detail below.

[0015] [A-1] (Component a) Polyorganosiloxane (Component a) polyorganosiloxane is a base polymer of peroxide-curable heat-cured rubber (HCR) and is represented by formula (A1).

[0016] [ka]

[0017] In formula (A1), R 1 represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an aliphatic unsaturated group. Specifically, R 1 is an alkyl group (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl), an aryl group (e.g., phenyl, tolyl, xylyl), an aralkyl group (e.g., benzyl, phenethyl), etc. Also, R is a monovalent substituted hydrocarbon group. 1 is an m-chloromethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, a 3-cyanopropyl group, a 3-methoxypropyl group, etc. In order to obtain easy synthesis and handling of the (component a) polyorganosiloxane and excellent heat resistance, in formula (A1), R1 It is preferable that 50% or more of the total of R are methyl groups, and particularly, 1 It is preferable that all of R are methyl groups. When heat resistance, cold resistance, or radiation resistance is required for the (component a) polyorganosiloxane, 1 In addition, when oil resistance and solvent resistance are required for the polyorganosiloxane (component a), R 1 As the alkyl group, it is preferable that the alkyl group contains a 3,3,3-trifluoropropyl group.

[0018] In formula (A1), R 2 represents an alkenyl group. Specifically, R 2 is a vinyl group, an allyl group, a 3-butenyl group, a 4-pentenyl group, a 5-hexenyl group, etc. (Component a) Polyorganosiloxane is easy to synthesize and handle, and addition reactions are easily carried out, so R 2 is preferably a vinyl group.

[0019] In formula (A1), R 3 are independent R 1 or R 2 That is, R 3 is R 1 (a monovalent unsubstituted or substituted hydrocarbon group that does not contain an aliphatic unsaturated group) and R 2 In order to improve reactivity, R 3 As mentioned above, part of 2 Preferably, the alkenyl group is the alkenyl group shown below:

[0020] In formula (A1), n ​​and m each represent the total number of randomly or block-polymerized repeating units. The sum of n and m plus 2, which is the number of terminal groups, (n+m+2) corresponds to the mass-average degree of polymerization.

[0021] The polyorganosiloxane (component a) may be a random copolymer in addition to a block copolymer. The polyorganosiloxane (component a) is preferably substantially linear, but may have some branching in the siloxane skeleton.

[0022] The mass average degree of polymerization (n+m+2) of the polyorganosiloxane (component a) is in the range of 1000 to 10000. If it is smaller than the lower limit, the necessary workability is not obtained, and sufficient mechanical strength is not obtained. If it is larger than the upper limit, polymerization becomes difficult. For this reason, the mass average degree of polymerization is preferably in the range of 2000 to 8000.

[0023] In the (component a) polyorganosiloxane, R 2 In order to form a crosslinked product, each molecule has two or more R 2 (R 3 R in the terminal unit shown as 2 The content per mass of R is 0.001 mmol / g or more and less than 2.0 mmol / g. If it is less than the lower limit, the strength of the crosslinked body may be insufficient. If it is more than the upper limit, the crosslinked body may become brittle. For this reason, in formula (A1), R 2 The content is preferably 0.005 mmol / g or more and 0.3 mmol / g or less, and more preferably 0.01 mmol / g or more and 0.1 mmol / g or less.

[0024] In the silicone rubber composition of this embodiment, the polyorganosiloxane (component a) may be of one type or of multiple types.

[0025] [A-2] (Component b) Weight loss inhibitor The weight loss inhibitor (component b) is added to prevent the generation of flammable low molecular weight siloxanes due to the decomposition of the polyorganosiloxane (component a) that constitutes the main chain of the silicone rubber when the silicone rubber is exposed to high temperatures. Examples of the weight loss inhibitor include an inorganic filler (component b1), a platinum compound (component b2), and a ligand (component b3) (a ligand that can coordinate with the platinum atom that constitutes the platinum compound (component b2)). [A-2-1] (Component b1) Inorganic filler (Component b1) The inorganic filler is at least one of crystalline silica (quartz), Fe3O4, and TiO2.

[0026] [A-2-2] (Component b2) Platinum compound The platinum compound (component b2) is chloroplatinic acid, a reaction product of chloroplatinic acid and alcohol, a platinum-olefin complex, a platinum-vinylsiloxane complex, a platinum-ketone complex, a platinum-phosphine complex, etc. Among these, a platinum-vinylsiloxane complex is preferred because it is compatible with the polyorganosiloxane (component a) and is easily dispersed, and a platinum-1,1,3,3-tetramethyl-1,3-divinyldisiloxane complex and a platinum-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane complex are particularly preferred. The platinum compound (component b2) may be one type or multiple types.

[0027] [A-2-3] (Component b3) Ligand The (component b3) ligand is a compound capable of coordinating with the platinum atom constituting the (component b2) platinum compound. The (component b3) ligand is, for example, a phosphite or a nitrogen-containing aryl compound. Specifically, the (component b3) ligand is preferably triphenyl phosphite or 2,2'-bipyridyl.

[0028] [A-3] (Component c) Crosslinking agent (Component c) the crosslinking agent is an organic peroxide.

[0029] Specifically, organic peroxides used as the crosslinking agent (component c) include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, dicumyl peroxide, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexyne, di-t-butyl peroxide, t-butyl peroxybenzoate, bis(4-t-butylcyclohexyl)peroxydicarbonate, and the like.

[0030] [A-4] (Component d) Reinforcing Silica The reinforcing silica (component d) is a powder of precipitated silica, fumed silica, calcined silica, etc. The reinforcing silica (component d) may be of one type or of multiple types.

[0031] (Component d) reinforcing silica is added to the silicone rubber composition to give it suitable fluidity and to give high mechanical strength to the silicone rubber, which is the crosslinked product of the silicone rubber composition. (Component d) reinforcing silica is added to the silicone rubber composition to give it suitable fluidity and to give high mechanical strength to the silicone rubber, which is the crosslinked product of the silicone rubber composition. In order to obtain the above functions, (Component d) reinforcing silica has a BET specific surface area (specific surface area measured by the BET method) of 50 m 2 / g or more 350m 2 It is preferable that the molecular weight is not more than 1 / g.

[0032] The reinforcing silica (component d) is preferably subjected to a hydrophobization treatment to hydrophobize the surface where silanol groups (Si-OH groups) are present, which makes it possible to effectively prevent the silicone rubber composition from increasing in viscosity or causing significant reversion to plasticity.

[0033] In the hydrophobic treatment of (component d) reinforcing silica, for example, an organic silicon compound is used as a surface treatment agent.Specifically, the organic silicon compound used as the surface treatment agent is hexaorganodisilazanes such as 1,3-divinyltetramethyldisilazane, 1,3-dimethyltetravinyldisilazane, and hexamethyldisilazane; organosilazanes such as octamethyltrisilazane and 1,5-divinylhexamethyltrisilazane; alkyltrialkoxysilanes such as methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, and butyltrimethoxysilane; dialkyldialkoxysilanes such as dimethyldimethoxysilane, diethyldimethoxysilane, dimethyldiethoxysilane, and diethyldiethoxysilane; vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(methoxyethoxy)silane, etc. alkenyltrialkoxysilanes such as divinyldimethoxysilane and divinyldiethoxysilane; trialkylalkoxysilanes such as trimethylmethoxysilane and triethylmethoxysilane; trialkenylalkoxysilanes such as trivinylmethoxysilane and trivinylethoxysilane; organochlorosilanes such as trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, vinyltrichlorosilane, divinyldichlorosilane and trivinylchlorosilane, and silane coupling agents such as chloropropyltrimethoxysilane, dimethylpolysiloxanes (including cyclic structures), low molecular weight polyorganosiloxanes whose ends are blocked with hydroxyl groups or alkoxy groups, and organohydrogenpolysiloxanes. The organic silicon compound used as the surface treatment agent may be a partial hydrolysis product of the above-mentioned substances. Among the above substances, it is particularly preferable to use silane coupling agents in which the substituent bonded to the silicon atom other than the hydrolyzable group is a methyl group, cyclic dimethylpolysiloxanes, low molecular weight polyorganosiloxanes whose ends are blocked with hydroxyl groups or alkoxy groups, and organosilazanes.

[0034] [A-5] (Component e) Foaming agent The foaming agent (component e) is added in order to obtain a silicone rubber foam from the silicone rubber composition by decomposing upon heating and generating gas.

[0035] The foaming agent (component e) preferably has a decomposition temperature of 50°C or higher and 250°C or lower. If the decomposition temperature is lower than the lower limit, handling is difficult and storage stability is poor. If the decomposition temperature is higher than the upper limit, productivity is reduced. For this reason, the decomposition temperature of the foaming agent is preferably 80°C or higher and 200°C or lower.

[0036] The (component e) blowing agent is, for example, an organic blowing agent. Specifically, the organic blowing agent is an azo compound such as azobisisobutyronitrile (decomposition temperature: 102°C), 1,1'-azobis(1-acetoxy-1-phenylethane) (decomposition temperature: 106°C), azodicarbonamide (decomposition temperature: 205°C), or a nitroso compound such as dinitrosopentamethylenetetramine (decomposition temperature: 203°C), N,N-dimethyl-N,N-dinitrosoterephthalamide (decomposition temperature: 105°C). The above blowing agents are decomposed by heating to a temperature higher than the decomposition temperature, and generate gas such as N2 gas or CO2 gas. The (component e) blowing agent may be one type or multiple types.

[0037] In order to adjust the foaming temperature, a regulator such as urea or an organic acid may be used in combination with the organic foaming agent.

[0038] [A-6] Combination [A-6-1] (Component b1) In the silicone rubber composition of the present embodiment, it is preferable that the inorganic filler (component b1) is added in an amount of 0.1 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the polyorganosiloxane (component a). If the proportion of the inorganic filler (component b1) added is less than the lower limit of this range, when the silicone rubber is exposed to high temperatures, the decomposition and generation of flammable low molecular weight siloxane cannot be sufficiently suppressed, and it may be difficult to suppress the weight loss of the silicone rubber. In addition, if the proportion of the inorganic filler (component b1) added is more than the upper limit of this range, the flexibility of the silicone rubber may be lost. For this reason, it is preferable that the inorganic filler (component b1) is added in an amount of 0.2 parts by mass or more and 200 parts by mass or less, and more preferably 0.5 parts by mass or more and 150 parts by mass or less.

[0039] [A-6-2] (Component b2) In the silicone rubber composition of this embodiment, the platinum compound (component b2) is added to the polyorganosiloxane (component a) so as to contain 1 ppm or more and 300 ppm or less of platinum atoms. If the proportion of the platinum compound (component b2) added is less than the lower limit of this range, the decomposition of flammable low molecular weight siloxane from the silicone rubber at high temperatures cannot be sufficiently suppressed, and it may be difficult to suppress the weight loss of the silicone rubber. In addition, if the proportion of the platinum compound (component b2) added is greater than the upper limit of this range, it may be difficult to achieve cost reduction. For this reason, the platinum compound (component b2) is preferably added to the polyorganosiloxane (component a) so that the platinum atoms are 1 ppm or more and 200 ppm or less, and more preferably 5 ppm or more and 150 ppm or less.

[0040] [A-6-3] (Component b3) In the silicone rubber composition of the present embodiment, the (component b3) ligand is preferably added in an amount of 1 mol to 40 mol per mol of platinum atom contained in the (component b2) platinum compound. If the addition ratio of the (component b3) ligand is less than the lower limit of this range, the decomposition of flammable low molecular weight siloxane from the silicone rubber at high temperatures cannot be sufficiently suppressed, and it may be difficult to suppress the weight loss of the silicone rubber. In addition, if the addition ratio of the (component b3) ligand is more than the upper limit of this range, the effect of suppressing the decomposition of low molecular weight siloxane becomes saturated. For this reason, the (component b3) ligand is preferably added in an amount of 1 mol to 20 mol per mol of platinum atom contained in the (component b2) platinum compound, and more preferably added in an amount of 2 mol to 15 mol.

[0041] [A-6-4] (Component c) In the silicone rubber composition of the present embodiment, the (component c) crosslinking agent is preferably added in an amount of 0.001 parts by mass or more and 10 parts by mass or less, based on 100 parts by weight of the (component a) polyorganosiloxane. If the addition ratio of the (component c) crosslinking agent is less than the lower limit of this range, sufficient crosslinking may not be obtained, resulting in insufficient strength. If the addition ratio of the (component c) crosslinking agent is more than the upper limit of this range, a problem may occur in which a long post-cure is required to remove the decomposition product of the (component c) crosslinking agent that is excessively mixed. For this reason, the (component c) crosslinking agent is preferably added in an amount of 0.01 parts by mass or more and 5 parts by mass or less, and more preferably added in an amount of 0.1 parts by mass or more and 1 part by mass or less.

[0042] [A-6-5] (Component d) In the silicone rubber composition of the present embodiment, the addition of (component d) reinforcing silica is optional, but it is preferable that 1 part by mass or more and 100 parts by mass or less are added relative to 100 parts by mass of (component a) polyorganosiloxane. If the addition ratio of (component d) reinforcing silica is less than the lower limit of this range, the mechanical strength of the silicone rubber may be insufficient. In addition, if the addition ratio of (component d) reinforcing silica is more than the upper limit of this range, the viscosity of the silicone rubber composition may increase, and the workability during molding may deteriorate. For this reason, it is preferable that (component d) reinforcing silica is added in an amount of 1 part by mass or more and 60 parts by mass or less, and more preferably 5 parts by mass or more and 50 parts by mass or less.

[0043] [A-6-6] (Component e) In the silicone rubber composition of the present embodiment, the foaming agent (component e) is preferably added in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the polyorganosiloxane (component a). If the foaming agent (component e) is added in an amount less than the lower limit of this range, the amount of gas generated by decomposition is insufficient, which may make it difficult to produce a silicone rubber foam. If the foaming agent (component e) is added in an amount greater than the upper limit of this range, the amount of gas generated by decomposition is large, which may cause deformation of the silicone rubber foam. For this reason, the foaming agent (component e) is more preferably added in an amount of 0.5 to 7 parts by mass.

[0044] [A-7]Other In addition to the above components, the silicone rubber composition of the present embodiment may contain other additives as necessary.

[0045] For example, when the silicone rubber composition of the present embodiment contains reinforcing silica (component d), it may contain a surface treatment agent (component f) to hydrophobize the silanol groups present on the surface of the reinforcing silica (component d). The surface treatment agent (component f) is a low-viscosity silicone oil, silicone resin, silane compound, etc., having a silanol group or an alkoxy group at the end. In particular, the surface treatment agent (component f) is preferably a polydimethylsiloxane having a silanol group at both ends, and has a mass average degree of polymerization of about 4 to 200. The blending ratio of the surface treatment agent (component f) is appropriately set according to the type and blending ratio of the reinforcing silica (component d), but is preferably in the range of 0.1 to 20 parts by mass, more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the reinforcing silica (component d).

[0046] In addition, the silicone rubber composition of the present embodiment may contain conductive fillers (carbon black, etc.), pigments, thixotropy imparting agents, viscosity modifiers for improving extrusion workability, ultraviolet protection agents, mildew inhibitors, heat resistance improvers, flame retardants, antioxidants, etc.

[0047] [B] Method for producing silicone rubber composition The silicone rubber composition of the present embodiment is prepared by kneading the respective components.

[0048] For example, when preparing the silicone rubber composition of this embodiment, first, (component a) polyorganosiloxane, (component b1) inorganic filler, (component b2) platinum compound, (component b3) ligand, (component d) reinforcing silica, and (component f) surface treatment agent are mixed uniformly using a kneader or the like. Furthermore, if necessary, the mixture is further kneaded in a heated state to perform a surface treatment of (component d) reinforcing silica with (component f) surface treatment agent. The resulting mixture is further kneaded with (component c) crosslinking agent at room temperature using a kneader or two-roll mill. This produces the silicone rubber composition of this embodiment.

[0049] When the silicone rubber composition of the present embodiment contains a foaming agent (component e), the polyorganosiloxane (component a), the inorganic filler (component b1), the platinum compound (component b2), the ligand (component b3), the reinforcing silica (component d), and the surface treatment agent (component f) are mixed uniformly in the same manner as described above, and the crosslinking agent (component c) and the foaming agent (component e) are mixed at room temperature using a kneader or a two-roll mill.

[0050] [C] Actions and Effects The silicone rubber composition of this embodiment contains (component a) polyorganosiloxane, (component b) weight loss inhibitor, and (component c) crosslinking agent. In the silicone rubber composition of this embodiment, the crosslinked product obtained by crosslinking the silicone rubber composition at a temperature condition of 300°C or less has a weight loss of 0.4 g / cm when heated from 30°C to 900°C at a temperature increase rate of 150°C / min in a nitrogen atmosphere. 3 (Component b) weight loss suppression is added so that the weight loss is less than 100%. In this embodiment, the components constituting the silicone rubber composition interact with each other, and the silicone rubber, which is a crosslinked product of the silicone rubber composition, is converted into a dense crosslinked product at high temperatures by promoting the bonding of the hydrocarbon groups and silicon atoms of the linear polyorganosiloxane constituting the silicone rubber. As a result, in this embodiment, the generation of cyclic low molecular weight siloxanes due to the decomposition of the siloxane bonds of the linear polyorganosiloxane is suppressed, and the weight loss of the silicone rubber is effectively suppressed.

[0051] Weight reduction is 0.4g / cm 3 When the crosslinked body of the silicone rubber composition is less than 0.4 g / cm, the crosslinked body of the silicone rubber composition can maintain its shape even when exposed to high temperatures. 3 When a crosslinked body having a cross-linking strength of less than 100 mm is used as a cushioning material between opposing components, the crosslinked body is capable of retaining its shape even after exposure to high temperatures, and therefore can function as a spacer between the opposing components, maintaining electrical insulation between the components, and suppressing heat propagation.

[0052] The same effects as above can also be obtained with a silicone rubber composition that further contains (component e) a foaming agent for producing a silicone rubber foam. EXAMPLES

[0053] Examples and Comparative Examples will be described below with reference to Tables 1 and 2. Each table shows the composition and test results of each example. In each table, (EX1) to (EX14) correspond to Examples, and (C EX1) to (C EX7) correspond to Comparative Examples.

[0054] [Table 1]

[0055] [Table 2]

[0056] [1] Regarding the materials used in the preparation of each silicone rubber composition The components used in preparing the silicone rubber composition of each example will be described below.

[0057] In the following description, the siloxane units are described using the following symbols.

[0058] M units: (CH3)3SiO 1 / 2 - M vi Unit: (CH3)2(CH2=CH)SiO 1 / 2 - M OH Unit: (CH3)2(OH)SiO 1 / 2 - D unit: -(CH3)2SiO- D vi Unit: -(CH3)(CH2=CH)SiO-

[0059] [1-1] (Component a) Polyorganosiloxane In each example, the following was used as the polyorganosiloxane (component a).

[0060] (a-1) M vi D n D vi m M vi (n=7980, m=22, 0.04mmol / g Vi) (a-2) MD n D vi m M (n=3660,m=340, 1.14mmol / gVi)

[0061] That is, in each example (component a-1), both ends are M v The intermediate units are D and D. vi The mass average degree of polymerization (n+m+2=7980+22+2) is 8004, and the vinyl group (R 2 The vinyl group content of the component a-2 is 0.04 mmol / g. In each example, the component a-2 is a polyorganosiloxane gum in which both ends are blocked with M units, and the intermediate units are D units and D units. vi It is a linear polydimethylsiloxane consisting of units, and has a mass average degree of polymerization (n+m+2=3660+340+2) of 4002 and a vinyl group (R 2 ) is a polyorganosiloxane gum having a vinyl group content of 1.14 mmol / g.

[0062] In each example, (component a-1) is R 1 is a methyl group, and R 2 is a vinyl group, and R 3 R 2 In each example, (component a-2) is a vinyl group, as in the above formula (A1). 1 is a methyl group, and R 2 is a vinyl group, and R 3 is a methyl group.

[0063] [1-2] (Component b) Weight loss inhibitor [1-2-1] (Component b1) Inorganic filler In each example, the following was used as the inorganic filler (component b1).

[0064] (b1-1) Crystalline silica (quartz) (product name: Crystalite VX-S; manufactured by Takimori Co., Ltd.) (b1-2) Fe3O4 (product name KN-320; manufactured by Toda Kogyo Co., Ltd.) ·(b1-3)TiO2 (Product name P-25; manufactured by EVONIK)

[0065] [1-2-2] (Component b2) Platinum compound In each example, the following was used as the platinum compound (component b2).

[0066] Platinum-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane complex (mass content of platinum atoms: 1.8%)

[0067] [1-2-3] (Component b3) Ligand ((Component b2) capable of coordinating with platinum atoms constituting platinum compounds) In each example, the following was used as the ligand (component b3).

[0068] (b3-1) Triphenyl phosphite (b3-2) 2,2'-bipyridyl

[0069] [1-3] (Component c) Crosslinking agent In each example, the following was used as the (component c) crosslinking agent.

[0070] 2,5-bis(t-butylperoxy)-2,5-dimethylhexane

[0071] [1-4] (Component d) Reinforcing Silica In each example, the following was used as (component d) reinforcing silica.

[0072] (Component d-1) Fumed silica (BET specific surface area 130 m 2 / g)(Product name aerosil 130; manufactured by EVONIK) (Component d-2) Fumed silica (BET specific surface area 200 m 2 / g)(Product name aerosil 200; manufactured by EVONIK) (Component d-3) Precipitated silica (BET specific surface area 185 m 2 / g) (Product name SIPERNAT 268; manufactured by EVONIK)

[0073] [1-5] (Component f) Surface treatment agent In each example, the following was used as the surface treatment agent (component f).

[0074] ·(component f−1)M OH D8M OH ·(component f-2)M OH D 30 M OH

[0075] In other words, (component f-1) and (component f-2) have M at both ends. OH It is a polysiloxane in which the intermediate unit is composed of D units.

[0076] [2] Preparation of silicone rubber compositions for each example The procedure for preparing the silicone rubber composition of each example will be described below.

[0077] In preparing the silicone rubber composition of each example, the components were mixed in the ratios shown in Tables 1 and 2. Specifically, first, (component a) polyorganosiloxane, (component b1) inorganic filler, (component d) reinforcing silica, and (component f) surface treatment agent were mixed using a kneader and kneaded in a heated state (150°C, 1 hour) to obtain a kneaded mixture. Then, after cooling the kneaded mixture to room temperature, (component b2) platinum compound, (component b3) ligand, and (component c) crosslinking agent were further kneaded into the kneaded mixture using a two-roll mill. In this way, the silicone rubber composition of each example was prepared.

[0078] Tables 1 and 2 show the parts by mass of components other than (component a) added relative to 100 parts by mass of (component a) polyorganosiloxane. In the "Composition" column of Tables 1 and 2, "-" indicates that the component is not added.

[0079] In addition, in Tables 1 and 2, the weight of the platinum atom in the platinum compound (component b2) is shown as a ratio (ppm) to the weight of the polyorganosiloxane (component a). Similarly, in Tables 1 and 2, the amount (mol) of the ligand (component b3) per 1 mol of the platinum compound (component b2) is shown.

[0080] [3] Preparation of silicone rubber for each example The procedure for producing the silicone rubber (crosslinked product of the silicone rubber composition) of each example will be described below.

[0081] The silicone rubber composition prepared as above was placed in a mold (20 cm long x 20 cm wide x 2 mm thick) and crosslinked under pressing for 10 minutes at a temperature of 170°C to obtain a silicone rubber sheet in which the silicone rubber composition was crosslinked. The silicone rubber sheet was then subjected to a post-cure treatment at a temperature of 200°C for 4 hours using a hot air circulation oven.

[0082] [4] Evaluation of each silicone rubber The evaluation of each example of silicone rubber will be described below.

[0083] Here, as shown in Tables 1 and 2, the weight loss of the silicone rubber in each example was evaluated.

[0084] When evaluating the weight loss of silicone rubber, a thermogravimetric differential thermal analyzer (product name TG / DTA6200; manufactured by SII Nano Technology Co., Ltd.) was used. Here, about 10 mg of the silicone rubber sheet prepared as described above was heated in a nitrogen atmosphere (nitrogen gas with a purity of 99.9995% by volume or more, flow rate 220 ml / min). When heating the silicone rubber, the temperature was increased from room temperature (30°C) to 1000°C at a heating rate of 150°C / min. Thus, the weight loss rate WL (%) at 900°C was measured for each silicone rubber example.

[0085] Then, for each example, the density of the silicone rubber DE (g / cm 3 ) to calculate the weight loss of silicone rubber per unit volume WM (g / cm 3 ) was sought.

[0086] WM=DE*WL / 100

[0087] FIG. 1 shows the weight loss of the silicone rubber (WM (g / cm 3 1 is a graph showing the relationship between the content of platinum atoms in the platinum compound (component c) relative to the polyorganosiloxane (component a), CL (ppm). In Fig. 1, diamond markers indicate the results of (EX1) to (EX14), and circular markers indicate the results of (C EX1) to (C EX7).

[0088] As shown in Tables 1 and 2 and in Figure 1, (EX1) to (EX14) (diamond markers in Figure 1) represent the weight loss of silicone rubber per unit volume, WM (g / cm 3 ) is 0.4g / cm 3 In contrast, (C EX1) to (C EX7) (circular markers in Fig. 1) show the weight loss of silicone rubber per unit volume WM (g / cm 3 ) is 0.4g / cm 3 Thus, (EX1) to (EX14) are able to reduce the weight loss WM of the silicone rubber per unit volume more than (C EX1) to (C EX7).

[0089] As described above, the silicone rubber compositions (EX1) to (EX14) have a weight loss of 0.4 g / cm when the crosslinked bodies obtained by crosslinking the silicone rubber compositions at a temperature of 300°C or less are heated from 30°C to 900°C at a heating rate of 150°C / min in a nitrogen atmosphere. 3 (Component b) weight loss suppression is added so that the weight loss is less than 100 parts by mass of (Component a) polyorganosiloxane. In particular, (Component b1) inorganic filler is added in an amount of 0.1 parts by mass or more and 200 parts by mass or less to 100 parts by mass of (Component a) polyorganosiloxane, (Component b2) platinum compound is added so that it contains 1 ppm or more and 300 ppm or less of platinum atoms to the (Component a) polyorganosiloxane, and (Component b3) ligand is added so that it contains 1 mol or more and 40 mol or less to 1 mol of platinum atoms contained in the (Component b2) platinum compound. Therefore, the components constituting the silicone rubber compositions of (EX1) to (EX14) interact with each other, and the silicone rubber, which is a crosslinked body of the silicone rubber composition, is effectively suppressed from decomposing flammable low molecular weight siloxane from the silicone rubber at high temperatures, and the weight loss of the silicone rubber is effectively suppressed.

[0090] In contrast, the silicone rubber compositions (C EX1) to (C EX7) differ from the silicone rubber compositions (EX1) to (EX14) in that the weight loss suppression of (component b) is 0.4 g / cm 3It is not added so that the ratio is less than 1. In particular, in the silicone rubber compositions (C EX1) to (C EX7), at least one of the blends of the inorganic filler (component b1), the platinum compound (component b2), and the ligand (component b3) does not satisfy the above relationship. Specifically, the silicone rubber composition (C EX1) does not contain the ligand (component b3). The silicone rubber composition (C EX2) does not contain the platinum compound (component b2) and the ligand (component b3). The silicone rubber composition (C EX3) does not contain the inorganic filler (component b1) and the platinum compound (component b2). The silicone rubber composition (C EX4) does not contain the inorganic filler (component b1). The silicone rubber composition (C EX5) does not contain the inorganic filler (component b1). The silicone rubber composition (C EX6) does not contain the inorganic filler (component b1). The silicone rubber composition (C EX7) does not contain the inorganic filler (component b1) and the ligand (component b3). Therefore, in the silicone rubbers which are crosslinked bodies of the silicone rubber compositions (C EX1) to (C EX7), unlike the cases of (EX1) to (EX11), the decomposition of flammable low molecular weight siloxanes from the silicone rubber at high temperatures is not inhibited, and the weight of the silicone rubber is significantly reduced.

[0091] <Other> Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Industrial Applicability]

[0092] According to this embodiment, it is possible to effectively prevent the decomposition of flammable low molecular weight siloxane from silicone rubber at high temperatures and to prevent the weight of silicone rubber from decreasing. Therefore, the present invention can be suitably used in various technical fields such as gaskets, cushioning materials, and O-rings, which require the above effects.

Claims

1. (Component a) Formula (A1) 【Chemistry 1】 (In formula (A1), R １ represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an aliphatic unsaturated group, R ２ represents an alkenyl group, R ３ are each independent R １ Or R ２ where n and m represent the total number of repeating units randomly polymerized or block polymerized, respectively, and n+m+2, which is the sum of n and m and the number of terminal groups (2), represents the mass average degree of polymerization. ２ The content per mass of the compound is 0.001 mmol / g or more and less than 2.0 mmol / g, and R ２ A polyorganosiloxane having two or more of the following: (Component b) a weight loss inhibitor, and (Component c) a silicone rubber composition containing an organic peroxide crosslinking agent, The silicone rubber obtained by crosslinking the silicone rubber composition has a weight loss of 0.4 g / cm when heated from 30° C. to 900° C. at a temperature increase rate of 150° C. / min in a nitrogen atmosphere. ３ is less than Silicone rubber composition.

2. The (component b) weight loss inhibitor, (Component b1) inorganic filler, (Component b2) a platinum compound, and (Component b3) Ligand Including, The ligand (component b3) is capable of coordinating with a platinum atom constituting the platinum compound (component b2). The silicone rubber composition according to claim 1.

3. (Component b3) The ligand is a phosphite or a nitrogen-containing aryl compound; The silicone rubber composition according to claim 2.

4. (Component b1) Inorganic filler is crystalline silica, Fe ３ O ４ Or TiO ２ That is, The silicone rubber composition according to claim 2.

5. The content of the inorganic filler (component b1) is 0.1 to 200 parts by mass per 100 parts by mass of the polyorganosiloxane (component a); The silicone rubber composition according to claim 2.

6. (Component b1) the platinum compound contains 1 ppm or more and 300 ppm or less of platinum atoms relative to (component a) the polyorganosiloxane; The silicone rubber composition according to claim 2.

7. The amount of the ligand (component b3) is 1 mol or more and 40 mol or less per 1 mol of platinum atoms of the platinum compound (component b2). The silicone rubber composition according to claim 3.

8. (Component d) Reinforcing Silica Further comprising: (Component d) reinforcing silica has a BET specific surface area of ​​50 m ２ / g or more 350m ２ / g or less, (Component a) is 1 part by mass or more and 100 parts by mass or less relative to 100 parts by weight of polyorganosiloxane, The silicone rubber composition according to claim 1.

9. A silicone rubber composition according to any one of claims 1 to 8, which is obtained by crosslinking the silicone rubber composition. Silicone rubber.

10. (Component e) further comprises a blowing agent; The silicone rubber composition according to claim 1.

11. A silicone rubber composition according to claim 10, which is obtained by crosslinking and foaming the silicone rubber composition. Silicone rubber foam.

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